KR100293612B1 - Nuclear power plant and its internal system command signal generation method - Google Patents

Abstract

The operator of the nuclear steam supply system manually selects either a feed pump lineup consisting of one, two or three main feed pumps for normal reactor operation to generate power. The selection sets or resets the status latch for each pump, indicating the intended pump operation. A system (RPCS) that executes a step of reducing the power output of the reactor comprises a logic circuit that combines a signal indicative of a tripping of one or more pumps with the pump state latch to produce the results described below: (a When one pump is selected, the trip of one pump does not generate an RPCS trip command signal (since the reactor will trip), and (b) if two pumps are selected, the trip of one pump While generating an RPCS trip command signal, (ii) a trip of the two pumps does not generate an RPCS trip command signal, and (c) if three pumps are selected, (i) a trip of one pump generates an RPCS trip command signal. Without generating (as the transient control can be controlled by the base control system), (ii) the trip of the two pumps generates the RPCS trip command signal, and (iii) the trip of the three pumps does not produce the RPCS trip command signal. .

Description

Nuclear power plant and its internal system command signal generation method

TECHNICAL FIELD The present invention relates to nuclear power plants, and more particularly, to the automatic response of a nuclear reactor control system to sudden and unexpected losses in the main components of a power plant.

The nuclear steam supply system (NSSS) of a pressurized water nuclear power plant typically operates with minimal power and circulation perturbation. The system is coordinated by a basic reactor control system. However, uneven generation of power plant imbalances can occur, such as large turbine load rejection, turbine trips, or partial loss of on-line main feed water pump capacity. have. Under the above conditions, maintaining the NSSS within the control band range may be done when rapidly reducing the NSSS power at a faster rate than normal fast control rod insertion. In addition, rapid NSSS power reduction is effective to obtain sufficient thermal margin for internal control rod deviations (including spurious rod drop) without reactor trips.

As a known system for this purpose, a Reactor Power Cutback System (RCCS) from Combustion Engineering, Windsor, Connecticut is commercially available. “Reactor Power Reduction System and Method” of US Pat. No. 4,075,059, filed February 21, 1978, describes the RPCS. The techniques disclosed in these patents are incorporated herein by reference. The system is designed to adjust for large load disposal, loss of feed pumps, or internal deviation of the control rods (including doctor rod drops) by providing a "step" reduction in reactor power. The step reduction in reactor power is done by simultaneously dropping one or more groups of preselected overall strength adjustment control rods into the core. The control rod group is dropped in the order of normal insertion. In addition, the RPCS provides a control signal to the turbine to maintain the reactor power and turbine rebalancing following an initial reduction in reactor power and to restore the steam generator water level and pressure to normal control values.

The conventional NSSS includes two variable speed main feed pumps and two steam generators that are split and deliver secondary coolant to a common conduit controlled at each value for each steam generator. If a loss of the steam generator feed pump occurs, the flow of secondary coolant to the steam generator is reduced and the remaining pump is unable to provide 100% of the feed water required by the steam generator. At this time, the steam generator consumes water faster (by changing the water to steam) than the water of the steam generator which can be replaced, thereby causing the level of water in the steam generator to continuously drop. This situation cannot be tolerated for a very long time before the reactor and the turbine trip with a signal indicating that the water level of the steam generator is low. However, if the reactor power immediately decreases rapidly enough to a sufficient extent, the steam generator's steam production capacity is reduced, thus preventing the reactor-turbine trip from lowering the water level of the steam generator. In a typical nuclear power plant provided with two feed pumps having 65% of the total feedwater supply capacity for each steam generator, the initial reduction required by the loss of one feedwater pump to avoid reactor trips is 75% of the total reactor power. The limited power that allows for continued reactor operation after the loss of the feed pump is determined by the capacity of the pump of the system and the characteristics of the steam generator.

In order to run the power plant, the feed pump is started manually by the power plant operator by providing steam and cooling water to the turbine driver or by powering the motor driver. The pump draws water and recycles it to the feed or concentrated storage tank. When the pump is running and checking for normal operation, the speed is manually set to the minimum control speed by the operator. If the power plant condition is automatically controlled by the feedwater control system by switching one or both of the feedwater pumps, the operator automatically switches the control mode of the selected pump (s). In automatic control, the feedwater control system sets the pump speed and maintains a control value position at a predetermined water level in the steam generator.

In the power plant, the feed pump and the RPCS are controlled in the following way.

TABLE l

The NSSS should be provided with three main feed pumps, and the third main feed pump may be spared or shared with the other two feed pumps. Conventional RPCS are easily incorporated into NSSS configurations with three main feed pumps, but the present invention improves RPCS logic with the advantage of greater operational flexibility possible with three pump NSSS.

It is therefore an object of the present invention to provide improved RPCS logic for NSSS with at least three main feed pumps.

Another object is that the RPCS logic distinguishes two pump lineups and three pump lineups when automatically generating an RPCS command signal.

According to the present invention, the operator of the NSSS manually selects a lineup of one, two, or three main feed pumps in normal reactor operation to produce power. The selection sets or resets a status latch for each pump that represents the desired pump operation. The logic circuit combines a signal inducing a trip of one or more pumps with the pump state latch to achieve the following results.

(a) If one pump is selected, the trip of the one pump does not generate an RPCS trip command signal (since the reactor will trip, for example to a low steam generator water level).

(b) If two pumps are selected, (iii) a trip of one pump generates an RPCS trip command signal, while (ii) a trip of the two pumps does not generate an RPCS trip command signal.

(c) If three pumps are selected, (i) the trip of one pump does not generate an RPCS trip command signal (since the transient is controlled by the base control system), and (ii) the trip of both pumps is an RPCS trip. The command signal is generated, and (iii) trips of the three pumps do not generate the RPCS trip command signal.

Preferably, the logic is executed redundant and assured sublogic. For example, each feed pump trip generates two independent feed pump trip signals. Likewise, each pump state selection enables two separate state latches. The pump trip signal and pump state latch are paired in separate logic gate arrays so that a particular one of the pumps selected for operation generates a redundant RPCS trip control signal. However, unless determined by the RPCS trip control signal generated by both of the logic gate array pairs, the RPCS does not trip.

The method includes a nuclear reactor, at least three feed pumps for supplying water to a steam generator, a control rod system for controlling the power output of the reactor core, and a portion of the control rod being rapidly inserted into the reactor core. It can be used in nuclear power plants with a system that reduces the power output from the initial level to a non-zero level with the loss of pump operation of at least one feed pump. The method selects which pumps the operator will run and which pumps will not run, generating command signals for the system for quickly inserting a portion of the control rod. The trip signal is generated from each of the pumps to be operated, which results in a loss of pump operation. The command signal to activate the system to quickly insert a portion of the control rod is generated only when the trip signal is generated by both but not one of the selected pumps.

1 is a functional logic diagram of a reactor power reduction system for a nuclear steam supply system.

2 is a logic diagram of a circuit for generating a reactor power reduction command signal due to the loss of one or more of the three main feed pumps in accordance with the preferred embodiment of the present invention.

* Explanation of symbols for main parts of drawings

12 Reactor Power Reduction System 14 Control Rod Drive Mechanism

104: feed pump trip signal unit 106: logic execution unit

108, 110: switch 112, 114: OR gate

122: AND gate

1 is a schematic illustration of a schematic 10 of functional components associated with a reactor power reduction system (RPCS) 12. When encountering any transient current during operation, the reactor power reduction system sends a control signal to the control rod drive mechanism 14 and reacts with the turbine control system 16 to bring the NSSS power level to a non-zero level. To stabilize. If the RPCS is unable to stabilize the NSSS by a combination of turbine runback and coordination of coordination control rod groups, the RPCS trips one or more control rod groups.

For the purposes of the present invention, the logic diagram relates to the condition under which the reactor power reduction system trip request signal is generated at the instruction block 18 for processing at the RPCS 12. The processing of the functional block 12 includes, for example, control rod selection criteria 20 that vary in accordance with the NSSS data provided by the sensor of the equipment. Other computational conditions of the NSSS are supplied from the block 24 to the RPCS 12. The RPCS 12 also operates in the reactor power reduction control panel 26 and an alarm is generated by the RPCS 12 to display in the alarm portion 28 of the operator console.

2 shows a pump select logic circuit 100 for three main feed pumps A, B, and C, which circuit (1) pump select and enable portion 102 and (2) feed pump It is divided into four functional units, such as the trip signal portion 104, (3) the logic execution portion 106, and (4) the RPCS trip request portion 18. The function of the command unit in FIG. 2 may be considered to be the same as the function of block 18 in FIG. 1 for the purpose of this description.

The part 102 comprises at least one switch 108 and at least one switch 110 for each main feed pump A, B, C, by which the operator can operate at the power plant. It is possible to choose whether to run a particular pump fully to produce regular power. When fully operational, pump speed control, for example above 5% power plant power, is automatically adjusted by an automatic feedwater control system (not shown). If not fully operated, the pump will either wait or stop service. Thus, the operator can specify, if necessary, which of the pumps is intentionally disabled from an automatically controlled operation. The automatic feedwater control system controls various pump speeds and value positions to maintain a predetermined water level in the steam generator. Although not regularly used in the operation of the NSSS, an operating pump may actually be in a "standby" condition, under manual control of the operator, the pump corresponding to the flow to the steam generator generated by the other pump Rotate at minimum circulation speed.

In the illustrated embodiment, the main water feed pump A can be toggled to its start or stop position manually, either at the main panel in the power plant control room associated therewith, or at a motor control center associated with the feed water pump system. Has a switch 108A.

"Start" corresponds to the choice to fully operate the pump. "Stop" refers to release from full operation, ie "off" or standby. As used herein, the term "operational" means "fully operational." The logic state of each switch 108A, 110A is conveyed by a pair of logic OR gates 112A, 114A, and its output is delivered to flip-flop circuit 116A. The output Q on line 118A of the circuit 116A becomes a logic " 1 " when the operator selects the start state for pump A at switch 08A or 110A. The logic " 1 " is passed to AND gate 120A, which acts as an enabling latch to indicate whether a particular pump state is active.

Each of the main feed pumps B, C has associated switches 108B and 108C, 110B and 110C, 112B and 112C, 114B and 114C, 116B and 116C, 118B and 118C, 120B and 120C.

Typically, the state latches are arranged redundantly so that the logic states at outputs 11A, 118B, and 118C are transferred to second AND gates 122A, 122B, and 122C, respectively. Thus, for example, if the operator manually selects the starting state for the main feedwater pump A via switch 108A or switch 110A, both latches 120A and 122A are excessively enabled.

Feed pump trip signal portion 104 responds to inputs from the main control panel labeled 126A, 126B, 126C and one or more feedwater control systems, labeled 128, respectively, the three main feed pumps labeled 124A, 124B, 124C, respectively. (A, B, C).

The water supply control system 128 and associated control logic for generating trip signals is not a configuration of the present invention. However, for each pump, such as 124A, the trip of the pump produces two trip signals 130A and 132A, which are delivered to latches 120A and 122A, respectively. Similarly, trip signals l30B, 132B and 130C and 132C are transmitted to latches 120B, 122B and 120C and 122C, respectively. When the inputs to any particular latch gate 120A, 120B, 120C, or 122A, 122B, l22C are all logic "1", each logic "1" output signal is a respective line 134A, 134B or 134C, or 136A. , 136B or 136C).

The logic execution portion 106 includes an RPCS trip control gate 138 that passes the RPCS trip control signal through the line 142 to the RPCS system 18 under certain conditions. Preferably, there is another RPCS trip control gate 140 through which a trip control signal is transmitted to the command block 18 via line 144. Thus, in the preferred embodiment, if no trip control signal is present on both lines 142 and 144, the actual RPCS trip command signal is not generated for delivery to the reactor power reduction system 12 (see FIG. 1). Do not.

The OR gate 138 receives signals from three AND gates 146, 148, 150. If any one of the three AND gates produces a logic "1" output, the gate 138 generates a control signal on line 142. Similarly, if the output of either of the AND gates 152, 154, 156 is a logic "1", as described above, the OR gate 140 passes a trip control signal on line 144. Let's do it. If only logic "1" is input to the AND gate from a signal corresponding to the conditions of two different pumps, each AND gate 146-156 generates a logic "1" output signal.

In the present invention, it is important to distinguish the initial conditions under which only two of the three feed pumps operate from the conditions under which all three feed pumps operate. The OR gates 160-182 located between the AND gate arrays 120, 122 and 146-156 serve as the RPCS trip command signal, for example, when only one of the two operating pumps is tripped, Only one of the three operating pumps serves to inhibit the generation of the trip command signal when tripping. In essence, the AND gates 146-156 require two of the three pump trip conditions to deliver a logic "1" signal to the OR gates 138, 140.

For example, if the main feed pump A is not in operation, i. E. Used preliminarily, the three pumps are identical to the tripped pump in the form of operation. Therefore, if both switches 110A and 110A are in a stop condition, the Q output signal of flip-flop 116A is logic "1" on line 158A. In this condition, the output signal Q is logic O, and therefore the gate 120A is not enabled. Nevertheless, the logic portion 106 has three pumps A, B, and C so that a predetermined trip control signal is generated on line 142 when one of the pumps (B or C) trips. Under the conditions of pumps A and B that trip during power plant operation, the same outputs should be produced for all to operate. Therefore, logic " 1 " from the Q output of flip-flop 116A can be passed to the OR gate 160, so that logic " 1 " can be passed to the AND gate 146. In the example of a trip of pump B, if AND gate 120B transfers a logic " 1 " through the OR gate 162 to AND gate 146, gate 146 is OR gate 138. And a logic " 1 " to the command portion 18 via line 142.

In the method, gate 146 responds to the conditions of both pumps A and B.

According to the overlap described above, the gate 152 is equally affected by the conditions of the pumps A and B. The outputs of gates 146 and 152 are (a) when pump A or B does not operate due to the "stop" setting of portion 102, and trips of pump B or A occur respectively, or (b) Both pumps A and B are operated as indicated by the "start" setting on the switch in part 102, and if a trip signal from both pumps A and B is generated, a logic "1" "Becomes.

In addition, if all pumps are operating in a consistent trip, the gates 138 or 140 do not both transmit an RPCS trip control signal to the trip command portion 18.

Under these conditions, the reactor fully trips at a low steam generator level, and as a result of the action of the RPCS 12, thus substantially reducing the power from the fission instead of simply lowering the power to a non-zero value. Reduce phosphorus.

In NSSS with three main feed pumps, each provides about 33.3% of the feed water required for the steam generator with a maximum capacity of at least each 50%. The reactor power reduction system according to the present invention is used in the following way.

TABLE 2

Thus, in the foregoing description, the RPCS operates only when at least two feed pumps are fully operational and the feed control system is in automatic mode. Conventional RPCS (early developed RPCS) operate when the reactor power is at least 50% (50%-60%) and the feedwater control system is in automatic mode. If the power is at least 50%, the water supply control system is always on. The relationship between the reactor power reduction system and the feedwater control system may vary. Preferably, the RPCS automatically detects (without operator adjustment) from the feedwater control system. The feed water control system of the feed pump is activated. Thus, the switch means for manually selecting which pump to operate in the pumping operation and designating which pump is released from the pumping operation may be the same switch means used by the operator in the control panel to operate the pump. If the wave level exceeds 50% and the RPCS is in operation, the RPCS "reads" the pump state previously selected by the operator. In addition, the RPCS can be designed to manually select which feed pump to operate via a switch specific to the RPCS when the power level is increased by about 50% and the RPCS is operating.

Those skilled in the art will appreciate that various modifications of the above described functions are possible. For example, it may be replaced by a programmable logic controller or other programmed logic via computer software.

Claims (5)

A nuclear reactor, at least one steam generator, a plurality of feed pumps for supplying water to the steam generator, a first system for inserting control rods into the core at a regular speed to control the power output of the reactor core, and a feed pump A second system comprising means for rapidly inserting a portion of the control rod into the reactor core at a speed faster than the normal speed to reduce the power output from the initial level to a non-zero level if nearly all of its pumping operation is lost. Pressurized water type nuclear power plant, In the nuclear power plant having three water feed pumps for the steam generator, Switch means for manually selecting which of the three pumps to pump on, and if necessary, to designate which of the three pumps to intentionally deactivate pumping; Means for generating a pump trip signal from each pump to be operated when a particular pump to be operated is almost lost in pump operation; Means in said second system responsive to said switch means and said pump trip signal generating means, Two pumps are selected and a pump trip signal is generated from only one of the selected pumps, or Means for generating a command signal to promptly insert some of the control rods only when three pumps are selected and a pump trip signal is generated from each of any two pumps but not all of the selected pumps. 2. The apparatus of claim 1, wherein the means responsive to the switch means and the pump trip signal generating means comprises: A flip-flop circuit associated with said switch means of each pump to produce a first signal on a first line if a pump is selected and a second signal on a second line if a pump is designated; An enable AND gate electrically connected to the first line of each of the flip-flop circuits and to the pump trip signal generating means, each of which delivers a logic "1" only when the first signal and the pump trip signal coincide; And an OR gate electrically connected to an output of each of said enable AND gates and to each of said second lines. 3. The apparatus of claim 2, wherein said means responsive to said switch means and said pump trip signal generating means comprises a logical ADN gate for each possible combination of two of said feed pumps, each logical AND gate being one. And an output of one of the OR gates connected to the second line associated with the pump of the other and an output of the other of the OR gates connected to the second line associated with the other pump. A nuclear reactor, at least two steam generators, three feed pumps for supplying water to the steam generator, a first system for inserting control rods into the core at a regular speed to control the power output of the reactor core, and at least one A second system comprising means for rapidly inserting a portion of the control rod into the reactor core at a speed faster than the normal speed to reduce the power output from the initial level to a non-zero level if the pumping operation of the feed pump of In the pressurized water type nuclear power plant comprising a, generating a command signal for the second system to quickly insert a portion of the control rod, Setting switch means to designate which of said three pumps to operate and, if necessary, to specify which of said three pumps to de-pump; Generating a pump trip signal from each of the pumps to be operated, where the pump operation suffers almost all losses; In response to the switch means setting and the pump trip signal, (a) if one pump is selected and tripped to operate, no command signal is generated, and (b) if both pumps are selected to operate, only the trip of one selected pump generates a command signal, and (c ) If three pumps are selected to operate, only under the condition that the trip of the two selected pumps generates a command signal, Generating a command signal instructing the second system to quickly insert a portion of the control rod. The method of claim 4, wherein The command signal generating step is executed in a logic circuit having a pump status latch associated with each pump, respectively, each latch having a condition indicating whether operation of each pump is required or not; And the step of setting the switch means generates an enable condition at each latch so that a trip signal from each pump can pass through the logic circuit.